The invention relates to assembly and packaging of signal processing devices, in particular to an electronic circuit unit that provides EMI shielding, is simple to assemble and provides good structural integrity.
Devices used in communication networks, such as routers or switches to name a few, are constructed as cabinets with a bay where a plurality of standard size electronic circuit units are inserted. The electronic circuit units all connect to a main circuit board, such as a backplane or a midplane, through which data is transferred from each electronic circuit unit to other components.
Electronic circuit units that are currently available suffer from a number of drawbacks. The most significant ones are complexity of assembly and poor structural integrity, which translates into poor connector alignment tolerances for components within the unit or between the unit and the main circuit board of the cabinet.
Against this background there exists in the industry a need to provide an electronic circuit unit that is relatively simple to assemble and at the same time provides good structural integrity.
In one broad aspect, the invention provides an electronic circuit unit for use in an electronic equipment cabinet. The electronic circuit unit has first and second opposite main walls including EMI absorbing material and a motherboard frame between the main walls, the motherboard frame including a plurality of wall segments also including EMI absorbing material.
A motherboard is mounted in the motherboard frame by a first locating retainer. The first locating retainer positions the motherboard such that it resides between the main walls of the electronic circuit unit. A signal-processing module forming at least a portion of the first main wall is removably mounted to the motherboard frame by a second locating retainer. The signal-processing module connects with the motherboard through an electrical connector having mating parts. The first and the second locating retainers are positioned relative to one another to allow the mating parts to align and mate when the signal processing module is fastened to said motherboard frame.
This electronic circuit unit is advantageous for a number of reasons. First, the electronic circuit unit is easier to assemble by virtue of the motherboard frame to which the motherboard is directly mounted. Secondly, the structural integrity of the electronic circuit unit is enhanced.
In one specific and non-limiting example of implementation, the motherboard frame is generally rectangular and made of metallic material. Both main walls are removably fastened to the motherboard frame by respective locating retainers. An optional feature that enhances the cooling capacity of the electronic circuit unit is to provide each main wall with a heat sink and to thermally couple the two main walls through the motherboard such that heat generated by a component associated to one of the main walls can be transferred to the other main wall.
In a second broad aspect, the invention provides a motherboard frame for an electronic circuit unit. The motherboard frame has a plurality of wall segments including EMI absorbing material and arranged in a plane of reference, the wall segments circumscribing a void area having first and second opposite open sides. The wall segments have first, second and third locating devices spaced from one another in a direction that is transverse to the plane of reference. The first locating device is capable of receiving a planar motherboard and placing the motherboard in the motherboard plane, parallel to the plane of reference and in a predetermined position between the second and third locating devices.
In a third broad aspect, the invention provides a combination including a motherboard frame and a motherboard. The motherboard frame has a plurality of wall segments including EMI absorbing material and arranged in a plane of reference, the wall segments circumscribing a void area having first and second opposite open sides. At least some of the wall segments carry first, second and third locating devices that are spaced from one another in a direction that is transverse to the plane of reference. The motherboard is generally planar and it has an outline generally corresponding to the outline of the void area such as to allow the motherboard to be mounted in the motherboard frame. The first locating device is capable of receiving the planar motherboard and locating the motherboard parallel to the plane of reference and in a predetermined position between the second and third locating devices. The second locating device and the outline of the motherboard have respective geometrical configurations such that the motherboard can be inserted in the motherboard frame from one of the open sides without interference from the second locating device.